In processing for obtaining correlation between images, a correlation processing apparatus calculates the normalized correlation value or the sum of the absolute differences (SAD) value between image pixels under consideration and obtains correlation between the image pixels from the value.
Calculation of the normalized correlation value or SAD value involves calculations on more than one image, which requires a huge amount of computation.
In order to speed up the calculation of the normalized correlation value or SAD value, parallel processing has been adopted in which normalized correlation values for multiple windows are calculated concurrently (See Patent Document 1).
[Patent Document 1] Japanese Laid-Open Patent Publication No. 10-134183
Another type of parallel processing has also been proposed in which a window and a texture are divided into subregions and normalized correlation values for the subregions are calculated concurrently to obtain the normalized correlation value between the texture and the window (See Patent Document 2).
[Patent Document 2] Japanese Laid-Open Patent Publication No. 2008-84034